Beranda > Jembatan keledai > Cara Mengingat Sinus sudut 30, 60, dan 90

Cara Mengingat Sinus sudut 30, 60, dan 90

Dalam fisika ketika mempelajari materi yang berhubungan dengan vektor, momen gaya, getaran, maupun gelombang peserta didik sering dihadapkan pada sudut-sudut istimewa seperti sin 30, sin 60, cos 30, sin 90, cos 90 dan sebagainya.

Pada saat proses pembelajaran berlangsung saya merasa anak didik telah menguasai sudut-sudut istimewa tersebut, karena setiap saya memberikan contoh soal kemudian menanyakan sin 3o,  secara serentak siswa menjawab “setengah…”.

Namun berbeda ketika saya menganalisis hasil ulangan, ternyata sebagian besar salahnya justru pada nilai sin, cos, maupun tangen sudut tersebut. Permasalahannya sepele sebenarnya yaitu terbalik. Saat dikonvirmasi ke peserta didik sebagian menjawab “Bingung pak kalau sudah banyak soal, antara  sin 30 dan sin 60 mana yang setengah …”

Ternyata apa yang saya perkirakan  ketika proses pembelajaran berlangsung tidak sesuai dengan hasil evaluasinya. Dari kejadian inilah akhirnya saya bercerita kepada peserta didik tentang pengalaman saya waktu sekolah dulu bagaimana cara mengingat nilai sin 30 dan 60 agar tidak terbalik.

Dulu saya pernah punya teman namanya “Chosanah”, anaknya banyak mulut dan sering tidak terkontrol bila ngomong. Dari sikapnya itu teman-teman yang lain kadang-kadang sambil bergurau mengatakan “Sinting kamu Nah” atau “Sinting-Nah”.

Terinspirasi pelajaran matematika tentang sin dan cos , akhirnya saya sering memanggilnya dengan sebutan Cosanah-Sintingah. Apa Artinya ?…

  • Cosanah = Cos  enampuluh setengah
  • Sintingah = sin tigapuluh setengah

Nah kalau kedua atau salah satu saja ingat maka yang lain tentu ingat. misal yang kita ingat Sintingah = Sin tigapuluh setengah, maka sin 60 pasti setengah akar tiga. kalau sin 60 setengah akar tiga, ya pasti cos 60 = setengah, karena nilainya kan setengah dan setengah akar tiga.

Kalau Sin sembilan puluh ? bagaimana,….suatu saat protes.

lalu saya jawab sekenanya, ..lho kamu kalau sore  suka nonton cerita sangaji di TVRI kan ?

Apa hubungannya ? gak nyambung sama pertanyaan tuuuu…., sahutnya.

Ya adaa..lah….. Sangaji itu kan  Sin sangangpuluh siji (sin sembilan puluh = 1).

Sambil tertawa Chosanah malah mengatakan saya gila,…..”gila kamu!”

Wah ternyata  orang sinting kalau temu sama orang gila malah dapat membuat cara ngapalin rumus nih.

Nah….Sejak saat itu peserta didik yang ketemu  saya tidak lagi mengenal nama saya, malah saya disebutnya sangaji

Yaa,….tidak apa-papa Sangaji kan Sin sangangpuluh siji.

Bagaimana…?, Anda suka dengan sangaji ? kasih komentar dong !

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  22. Mulyata
    Januari 6, 2013 pukul 12:19 am

    Dear Kang Guru…..
    Saya hanya ingin Brainstormung aja mengenai hapalan sudut sudut istimewa dalam trigonometri.Saya mencoba untuk mengingat secara sederhana saja tentang suut 30 derajat.Segitiga siku siku yang salah satu sudutnya 30 derajat,maka sisi depannnya bernilai 1, sisi miringnya bernilai 2.Otomatis sisi Cos nya adalah akar 3(berdasar hukum Phytagoras).Sehinggga otomatis kita dapat menghapal dua sudut istimewa yaitu 30 dan 60 derajat, sekaligus paham dari sinus sd cotangen….dst.dari 0 derajat sd 360 derajat.

    Wasalam
    Mulyata.

  23. wiwin
    Februari 27, 2012 pukul 5:46 am

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  24. Desember 22, 2011 pukul 10:49 am

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  25. Brian
    September 18, 2011 pukul 1:35 pm

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  27. Juli 19, 2010 pukul 12:45 am

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  28. Juni 19, 2010 pukul 9:09 am

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    • Juni 19, 2010 pukul 9:18 am

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